- A
Use an RDS single-AZ instance and periodically restore from automated backups if needed.
Why wrong: Single-AZ deployments do not provide automatic failover for an AZ outage. Restoring from backups requires manual or scripted intervention, increasing downtime.
- B
Deploy the RDS PostgreSQL instance as Multi-AZ with automatic failover enabled.
Multi-AZ RDS maintains a standby instance in a different AZ. If the primary fails, RDS performs automatic failover, preserving the same database endpoint behavior.
- C
Create a read replica in a different AZ and use it only when the primary fails.
Why wrong: A read replica does not automatically replace a failed primary instance. You would need manual promotion and application rerouting.
- D
Use RDS with Multi-AZ disabled, but increase storage IOPS to prevent failover.
Why wrong: Performance changes do not address AZ availability. Storage IOPS does not provide automatic failover capabilities during an Availability Zone outage.
SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs its customer-facing web app on EC2 behind an Application Load Balancer. The database is Amazon RDS for PostgreSQL. The requirement is that if a single Availability Zone fails, the database must automatically fail over within the same AWS Region with minimal application changes. Which database setup best meets this requirement?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Deploy the RDS PostgreSQL instance as Multi-AZ with automatic failover enabled.
Option B is correct because RDS Multi-AZ for PostgreSQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary AZ fails, Amazon RDS automatically fails over to the standby, typically within 60–120 seconds, with no changes required to the application's connection string (the DNS name remains the same). This meets the requirement for minimal application changes and automatic failover within the same Region.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use an RDS single-AZ instance and periodically restore from automated backups if needed.
Why it's wrong here
Single-AZ deployments do not provide automatic failover for an AZ outage. Restoring from backups requires manual or scripted intervention, increasing downtime.
- ✓
Deploy the RDS PostgreSQL instance as Multi-AZ with automatic failover enabled.
Why this is correct
Multi-AZ RDS maintains a standby instance in a different AZ. If the primary fails, RDS performs automatic failover, preserving the same database endpoint behavior.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a read replica in a different AZ and use it only when the primary fails.
Why it's wrong here
A read replica does not automatically replace a failed primary instance. You would need manual promotion and application rerouting.
- ✗
Use RDS with Multi-AZ disabled, but increase storage IOPS to prevent failover.
Why it's wrong here
Performance changes do not address AZ availability. Storage IOPS does not provide automatic failover capabilities during an Availability Zone outage.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a read replica (which requires manual promotion and DNS changes) with a Multi-AZ standby (which provides automatic, transparent failover), leading them to incorrectly select Option C.
Detailed technical explanation
How to think about this question
RDS Multi-AZ uses synchronous replication to the standby instance, ensuring zero data loss (durable commit) during failover. The failover is triggered by Amazon RDS health checks that detect loss of connectivity to the primary, and the DNS record is automatically updated to point to the standby. In a real-world scenario, if the primary AZ experiences a power outage, the application experiences a brief connection interruption (typically under 2 minutes) but resumes without any code changes, which is critical for customer-facing web apps.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Resilient Architectures — This question tests Design Resilient Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy the RDS PostgreSQL instance as Multi-AZ with automatic failover enabled. — Option B is correct because RDS Multi-AZ for PostgreSQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary AZ fails, Amazon RDS automatically fails over to the standby, typically within 60–120 seconds, with no changes required to the application's connection string (the DNS name remains the same). This meets the requirement for minimal application changes and automatic failover within the same Region.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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